1. Field of the Invention
The present invention relates to a method for interpreting data used for clinical diagnostic purposes. In particular, a decision tree is disclosed for interpreting tandem mass spectrometry data relating to the quantification of metabolites used for diagnosing newborn babies.
2. Description of the Related Art
Automated methods for assessing a patient's condition are known. Computerized systems can be integrated to produce data that can be compared to a known result to allow for proper diagnosing. Such data might be produced by a MRI or CAT scanner, which is used to identify components within the human body.
One particular instrument used for identifying components of interest, whether they are of medicinal or chemical interest, is the mass spectrometer. In reference to U.S. Pat. No. 5,453,613, compounds, when introduced to the electrospray tandem mass spectrometer, are ionized and essentially fragmented. Each fragment produces a peak having local maximums that are matched to reference spectra. A compound can be identified by its associated fragments, each having a mass to charge ratio, which is then relative to the concentrations-of each fragment. All of the reference spectra and compound names can then be stored in a library for correlation and determination. Thus, mass/charge ratios can be used to identify components from known spectra stored in a database.
More recently, however, the use of spectrometry has been implemented in the field of clinical diagnosis. See Chace, U.S. application Ser. No. 09/277,119.
Inborn errors of metabolism usually result from defective enzymes or cofactors. Resulting genetic disorders can be diagnosed by the metabolic profiling of amino acids and acylcarnitines taken from blood spots subjected to a sampling protocol and thereafter introduced into an electrospray tandem mass spectrometer. An electrospray tandem mass spectrometer is very sensitive and specific and can detect a broad spectrum of disorders at the genetic level. With proper standards, data produced from the spectrometer includes values for particular metabolites. The metabolites that are of interest in detecting these disorders are, in particular, amino acids and acylcarnitines/carnitines and the derivatives thereof.
The spectra and resulting concentration values of each metabolite, as derived from mass spectrometry, are then compared to thresholds as a means for evaluating the contents of the blood sample. These thresholds determine the appropriate course of action necessary as a follow-up to the spectral analysis.
As seen in Wright et al., U.S. Pat. No. 5,545,895, spectrometry data is applied to a computerized search database for matching each component as a means of identification. In a clinical diagnostic setting, there must be further methods for evaluation beyond just that of the identification itself. The numbers must be quantified. Newborns can be born with metabolic disorders, which, if not treated within days, can result in death. Thus, after obtaining MS/MS (tandem mass spectrometer) data from blood samples from newborns, generally of the age of less than seven days old, there is a need for efficiently interpreting this data in relation to pre-determined metabolite concentration thresholds. This interpretation allows for proper decision-making necessary for the diagnosing and follow-up testing of newborns.